Look: Derbyshire knows zilch about Catholicism or Vatican II, has not carefully read anything the pope has said about relativism, and is not interested in doing any of the intellectual work required to remedy his ignorance. His posts make these points pretty clear. You can't have a good-faith conversation with him on these topics, so don't try.
Reading Derb on these matters, I find it very hard to think he's writing in bad faith. In fact, he outs the fact that Ponnuru and K-Lo basically want Vatican II undone. As does this papacy, in certain critical respects, especially with respect to the capacity of Catholics to question some non-binding aspects of faith in order to understand it better. Of course, there are points at which reason must cede to faith. But one gets the very powerful sense from Benedict and his acolytes that he simply wants reason to submit to ... him.